Ragefire Chasm was first discovered by Chief Goblin Engineer Gazlowe, during Rexxar’s visit to Orgrimmar. Beneath the city of Orgrimmar lies this fiery chasm. Recently, a clan of troggs known as Ragefire Troggs have begun to appear in the chasm, from deep below the lava-filled tunnels. Magatha the Seer, of the tauren people, attempted to make peace with these creatures, but was met only with hostility. It was clear that these troggs were not interested in diplomacy, and could potentially overwhelm the entire Horde if left unchecked.
A sect of the mysterious Shadow Council has also taken refuge in this chasm. This sect is known as the Searing Blade, and is led by Taragaman the Hungerer, a felguard; Jergosh the Invoker, a powerful warlock; and Bazzalan, a satyr. From their dark hiding place, they plot to overthrow and destroy all that the Horde has built for themselves in these lands.
From old World Dungeons site:
Ragefire Chasm consists of a network of volcanic caverns that lie below the orcs’ new capital city of Orgrimmar. Recently, rumors have spread that a cult loyal to the demonic Shadow Council has taken up residence within the Chasm’s fiery depths. This cult, known as the Burning Blade, threatens the very sovereignty of Durotar. Many believe that the orc Warchief, Thrall, is aware of the Blade’s existence and has chosen not to destroy it in the hopes that its members might lead him straight to the Shadow Council. Either way, the dark powers emanating from Ragefire Chasm could undo all that the orcs have fought to attain.